Field of the Invention
The present invention relates to a plugged honeycomb structure, and more particularly, it relates to a plugged honeycomb structure in which when the plugged honeycomb structure is used as a filter to trap a particulate matter and the filter is regenerated by burning and removing the particulate matter, the particulate matter hardly remains unburnt in both a circumferential portion and a central portion of the filter, and the number of times to regenerate the filter can be decreased as compared with a conventional plugged honeycomb structure.
Description of Related Art
An exhaust gas discharged from an internal combustion engine such as a diesel engine, each type of combustion device or the like includes a large amount of particulate matter (hereinafter also referred to as “PM”) mainly composed of soot. When this PM is discharged as it is into the air atmosphere, an environmental pollution is caused. Therefore, in an exhaust system for the exhaust gas, a particulate filter to trap the PM is mounted. An example of the particulate filter is a diesel particulate filter (DPF) for use in purification of the exhaust gas discharged from the diesel engine.
In such a DPF, there is used, for example, a honeycomb structure having porous partition walls defining a plurality of cells which become through channels for the exhaust gas. In this honeycomb structure, plugging portions to plug open ends of cells are disposed in the open ends of the predetermined cells in an end face on an outflow side of the fluid and the open ends of the residual cells in an end face on an inflow side of the fluid, and hence this honeycomb structure is utilized as a plugged honeycomb structure. Hereinafter, a particulate filter such as the DPF in which the plugged honeycomb structure is used will generically be referred to as “a honeycomb filter” sometimes.
As the honeycomb structure for use in the DPF or the like, there has been suggested, for example, a honeycomb structure of a segmented structure formed by bonding a plurality of honeycomb segments (e.g., see Patent Documents 1 and 2).
In a honeycomb filter such as the DPF, a pressure loss gradually increases due to the PM deposited in the filter with an elapse of time, and hence the PM deposited in the honeycomb filter is periodically burnt and removed to regenerate the filter sometimes. For example, as a method of regenerating the DPF, a regenerating method is known in which a temperature of the exhaust gas discharged from the engine is raised to heat the DPF by use of the exhaust gas at the high temperature. An example of a method of raising the temperature of the exhaust gas is a method in which by post jetting to temporarily excessively jet a fuel in a latter half of an explosion stroke or in an exhaust stroke, the excessive fuel is burnt to raise the temperature of the exhaust gas.
[Patent Document 1] JP-A-2003-10616
[Patent Document 2] JP-A-2003-254034